Method of lining cylinders



Dec. 29, 1 970 c. w. LINDQUIST 3,551,188

METHOD OF LINING CYLINDERS Filed Dec. 7, 1967 INVENTOR. CL/FFQQDHZL/A/DQU/ST BY gum] PM ATTORNEY.

3,551,188 METHOD OF LINING CYLINDERS Clifford W. Lindquist, Oil City,Pa., assignor to United States Steel Corporation, a corporation ofDelaware Filed Dec. 7, 1967, Ser. No. 688,770

Int. Cl. B4411 1/00 US. Cl. 117-97 5 Claims ABSTRACT OF THE DISCLOSUREThis invention relates to an improved centrifugal method of lining ametal cylinder with an iron-base hard material.

Conventional practice in lining a metal cylinder cen trifugally with alow-melting alloy is to place small pieces of the lining material in thecylinder, heat the cylinder to melt the lining material, and rotate thecylinder rapidly to distribute the molten material by centrifugal force.Each piece is of the same composition as the ultimate lining. Brown Pat.No. 1,923,075 describes a typical lining method which operates in thisfashion. Such methods commonly are used for applying a hard facingmaterial to the inside of a steel cylinder which is subject to wear, forexample the barrel of a reciprocating pump. Mild steel of which thecylinder usually is formed melts at about 2750 F., but the cylindercannot be heated beyond about 2500 F. without distorting it. Hence thismethod has been used only for lining cylinders with alloys which meltbelow this temperature. To the best of my knowledge, it has not beenused successfully with iron-base alloys of such metals as chromium,molybdenum or vanadium. Chromium alloys in particular form a desirablelining material for pump barrels because of their resistance tocorrosion. I recognize that the Brown patent describes the use of acobalt-chromium alloy. My own experience leads me to doubt this can bedone, but in any event such an alloy is far more costly than aniron-base alloy.

One practice in lining cylinders with higher-melting iron-base alloyshas been to melt the lining material separately, pour it into a heatedcylinder, and cast the lining in place centrifugally. This practicenecessitates the use of separate melting facilities, and does not assurea metal lurgical bond between cylinder and lining. It also results in anunfavorable stress pattern in the lining alloy, and the lining may crackin service. An alternative has been to form the liner as a separatepiece which is shrinkfitted within the cylinder. This necessitates anunduly heavy liner and of course produces no bond at all.

An object of my invention is to provide an improved centrifugal liningmethod which broadens the choice of lining materials to includeiron-base alloys of high-melting components, yet allows the liningmaterial to be melted within the cylinder.

A further object is to provide an improved lining method which affords afavorable stress balance with high-melting components in an iron-baselining material, that is, the lining material is in compression.

A more specific object is to provide an improved lining United StatesPatent 0 method in which a relatively low-melting iron-carbon eutecticalloy is used as a solvent, and higher-melting materials, such aschromium, molybdenum or vanadium, are dissolved in the eutectic after itmelts.

In the drawing:

The single figure is a diagrammatic vertical section of a cylinderprepared for lining in accordance with my method.

The drawing shows a cylinder 10 of a metal such as mild steel. I placewithin the cylinder a charge which consists of small pieces 12 ofiron-carbon alloy of a composition approaching the eutectic (about 4.3%carbon) and small pieces 13 of higher-melting alloys. The proportionsmay vary from about 25 to percent by weight of iron-carbon alloy and theremainder the high-melting alloys. These may include ferrochrome,ferro-molybdenum, ferrovanadium, etc. or various combinations inproportions calculated to produce a lining of the desired composition. Icover the ends of the cylinder with plugs 14 and 15, preferably weldedthereto. Plug 15 has a vent opening in which I mount a short-length tube16. I evacuate the cylinder through this tube and seal the tube toproduce nonoxidizing conditions within the cylinder. Optionally, I maycharge an inert gas to the cylinder be fore sealing it, particularly ifthe cylinder is of large diameter.

Next I heat the cylinder to melt first the iron-carbon alloy pieces 12,which melt at about 2085 F. The molten iron-carbon alloy dissolves thepieces 13 of higher-melting alloys. I continue to heat the cylinder asthe melting point of the solution rises as more and more of high-meltingalloy dissolves. The melting point of the solution reaches a maximumbelow about 2400 F. when all the alloy has dissolved. I may use anyappropriate means for heating the cylinder, such as high-frequencyinduction furnace or a conventionally fired fuel furnace. I rotate thecylinder slowly while heating it so that the charge Wets the full insidesurface of the cylinder as it melts. This assures a true metallurgicalbond between the lining and cylinder.

Next I place the cylinder containing the molten charge in a lathe orequivalent device and spin it on its axis. Centrifugal force distributesthe lining material over the inside surface, where it solidifies. I coolthe cylinder slowly, for example in ground mica or in a cooling furnace,to leave the solidified lining soft enough to be machined. I removeplugs 14 and 15 and machine the lining to its final dimension, afterwhich I reheat the cylinder to about 1900 F. and air-cool it. Theresulting lining not only is hard and corrosion-resistant, but ismetallurgically bonded to the cylinder and has a favorable stresspattern.

Specific examples of my invention are as follows:

EXAMPLE I I place within a mild steel cylinder 25 inches in length and 6inches diameter 25 pounds of a charge made up of small pieces of acomposition as follows:

Pounds Iron-carbon eutectic alloy 12.55 Alloy consisting of 4.5% C,67.0% Cr, remainder Fe and incidental impurities 4.50 Alloy consistingof 0.05% C, 70.50% Cr, remainder Fe and incidental impurities 7.10 Alloyconsisting of 60% Mo, remainder Fe and incidental impurities 0.85

I plugged the ends of the cylinder and evacuated it. I heated thecylinder in an induction furnace to a temperature of about 2400 F.,while slowly rotating it. I spun the cylinder in a lathe, cooled itslowly in ground mica, removed the plugs, machined the lining, reheatedthe cylinder to 1900 F., and air-cooled it. The resulting lining had athickness of inch and was metallurgically bonded 3 to the cylinder andwas in compression. The lining had a composition 2.7% C, 27.6% Cr, 1.8%M0, and the remainder iron and incidental impurities.

EXAMPLE II I repeated the foregoing procedure with similar materialsexcept that I substituted for the molybdenum alloy an alloy consistingof 55% V and the remainder iron and incidental impurities. The resultswere similar. The composition of the final lining was 2.7% C, 27.6% Cr,2.0% V, and the remainder iron and incidental impurities.

From the foregoing description it is seen that my invention affords aneffective and simple method of lining cylinders with higher-meltingiron-base alloys. There is no need to use as a charge material arelatively expensive alloy made up of the final composition of thealloy, but instead the charge can consist largely of low-cost ironcarboneutectic. To the best of my knowledge, the only way described in theprior art of producing a lining high in chromium by melting in thecylinder and spinning is to use the extremely high-cost cobalt-chromiumalloy as in the Brown patent. I believe it is an unexpected result thatI attain a favorable stress pattern as opposed to a dual-cast cylinderin which molten lining material is poured into the cylinder.

While I have described only certain preferred ways of practicing myinvention, it is apparent further modifications may arise. Therefore Ido not wish to be limited by the disclosure set forth, but only by thescope of the appended claims.

I claim:

1. A method of lining a steel cylinder with an ironbase hard facingmaterial comprising:

placing within the cylinder a charge which consists of small pieces ofiron-carbon alloy of a composition approaching the eutectic and smallpieces of at least one higher-melting alloy of the group consisting offerrochrome, ferromolybdenum, ferrovanadium and combinations thereof;

the proportions being 25 to 75 percent iron-carbon alloy and theremainder high-melting alloys;

sealing the ends of said cylinder and evacuating it;

heating the cylinder to a temperature about 2085 F. to

melt first the iron carbon alloy;

continuing to heat the cylinder as the molten ironcarbon alloy acts as asolvent for the higher-melting alloys, while the melting point of thesolution rises but reaches a maximum below about 2400 F. when all thehigher-melting alloys have dissolved; spinning the cylinder containingthe molten charge to distribute the charge by centrifugal force; andcooling the cylinder to solidify the resulting lining.

2. A method as defined in claim 1 in which the cylinder is slowlyrotated as it is heated to enable the molten charge to wet the innersurface and assure a metallurgical bond between the lining and cylinder.

3. A method as defined in claim 1 in which the cylinder is cooled slowlyto leave the lining soft enough to be machined and subsequently isreheated to about 1900 F. and air-cooled.

4. A method as defined in claim 1 in which the lining is in compressionto afford a favorable stress pattern.

5. A method as defined in claim 1 in which an inert gas is charged tothe evacuated cylinder before it is sealed.

References Cited UNITED STATES PATENTS 7/1965 Vordahl 164-80 8/1933Brown 11796

